<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>NaN - 非数字值</title>
</head>

<body>
    <p>一个数字除以一个字符串结果不是一个数字</p>
    <p>一个数字除以一个字符串数字结果是一个数字</p>
    <p id="demo"></p>
    <script>
        var x = 1000 / "Apple";
        var y = 1000 / "1000";
        document.getElementById("demo").innerHTML = isNaN(x) + "<br>" + isNaN(y);
    </script>
</body>

</html>